One Piece Episode 945 featured Straw Hat Pirates captain Monkey D. Luffy finally unlocking the technique that he’s been wanting to learn since he arrived at the Excavation Labor Camp in Udon. To save himself and the life of his friend, Old Man Hyo, Luffy used Ryuo to remove the collars wrapped around their necks before they exploded and killed them.
The future Pirate King managed to activate Ryuo as an act of desperation. After taking down Beast Pirates All-Star Queen the Plague, Big Mom Pirates captain and Emperor Charlotte Linlin made Luffy and Old Man Hyo her next targets when she learned that they were the ones who consumed all the red-bean soup in Udon. Luffy tried to stop Emperor Big Mom from attacking them because if they fell out of the ring, their collars would automatically blow up.
Unfortunately, lady Yonko was too angry to have mercy on them. She smashed them full force and ended up destroying the entire ring. Luckily, before Luffy and Old Man Hyo touched the ground, the Straw Hat Pirates captain unknowingly used Ryuo and got rid of the collars.
Ryuo is the term used by the citizens of the Land of Wano for Busoshoku Haki, a form of Haki that allows the user to use their own spiritual energy to create, in essence, an invisible armor, providing incredible offensive and defensive capabilities.
After they safely landed on the ground, he was noticeably surprised by what happened and admitted that he had no idea how he managed to activate Ryuo. Luffy happily stood up and told Old Man Hyo to run away with him, but Linlin resumed attacking them. Old Man Hyo, who is currently serving as Luffy’s Ryuo master, was about to follow the Straw Hat Pirates captain, but he decided to stop running away from the enemy.
He agreed to put his own life on the line to help Luffy learn Ryuo. Though he’s aware that he could die if he’s hit by Emperor Big Mom, he told the Straw Hat Pirates captain to remember the feeling he had when he unleashed Ryuo and to try protecting him against Linlin. He said that a moment of crisis would enable him to access his true power. Without a second thought, Luffy bravely stood up in front of Old Man Hyo and prepared himself to engage in an intense clash against one of the Four Emperors of the Sea.